Members of the Native American community have labeled the comments offensive. Some Democrats and advocates view them as racist.

Warren was quick to denounce the president's rhetoric. In an interview on MSNBC, she called it "deeply unfortunate."

"This was supposed to be an event to honor heroes, people who put it all on the line for our country, who, because of their incredible work, saved the lives of countless Americans and our allies," Warren said. "It is deeply unfortunate that the president of the United States cannot even make it through a ceremony honoring these heroes without having to throw out a racial slur."

Press secretary Sarah Huckabee Sanders told press that the nickname was not derogatory. Speaking at the White House daily press briefing, Sanders asserted that the label was "not a racial slur."

After being listed as Native American at Harvard University, Warren faced scrutiny over her ancestry during and after her 2012 campaign for Senate. Though she self-identifies as a Cherokee and Delaware Indian descendant, some critics say there is not sufficient evidence of her lineage.

She and Trump have feuded bitterly, with tensions only escalating during Trump's ascent to the Oval Office. With Warren an outspoken supporter of Democratic nominee former Secretary of State Hillary Clinton, the pair traded increasingly harsh insults over Twitter.